bundles/org.simantics.graphviz/src/org/simantics/graphviz/continuation/Computation.java

   1 package org.simantics.graphviz.continuation;\r
   2 \r
   3 import java.util.ArrayList;\r
   4 import java.util.concurrent.CancellationException;\r
   5 import java.util.concurrent.CountDownLatch;\r
   6 \r
   7 public abstract class Computation<T> {\r
   8     T result;\r
   9     Exception exception;\r
  10     ArrayList<Continuation<T>> continuations = new ArrayList<Continuation<T>>(); \r
  11     CountDownLatch doneGate = new CountDownLatch(1); \r
  12 \r
  13     public void addContinuation(Continuation<T> continuation) {\r
  14         synchronized(doneGate) {\r
  15             if(doneGate.getCount() == 0) {\r
  16                 if(exception == null)\r
  17                     continuation.succeeded(result);\r
  18                 else\r
  19                     continuation.failed(exception);\r
  20             }\r
  21             else\r
  22                 continuations.add(continuation);\r
  23         }\r
  24     }\r
  25 \r
  26     public boolean isDone() {\r
  27         return doneGate.getCount() == 0;\r
  28     }\r
  29     \r
  30     protected void failWith(Exception exception) {\r
  31         this.exception = exception;\r
  32         ArrayList<Continuation<T>> cs;\r
  33         synchronized (doneGate) {\r
  34             cs = this.continuations;\r
  35             this.continuations = null;\r
  36             doneGate.countDown();\r
  37         }\r
  38         if(cs != null)\r
  39             for(Continuation<T> continuation : cs)\r
  40                 continuation.failed(exception);\r
  41     }\r
  42     \r
  43     protected void doneWith(T result) {\r
  44         this.result = result;\r
  45         ArrayList<Continuation<T>> cs;\r
  46         synchronized (doneGate) {\r
  47             cs = this.continuations;\r
  48             this.continuations = null;\r
  49             doneGate.countDown();\r
  50         }\r
  51         if(cs != null)\r
  52             for(Continuation<T> continuation : cs)\r
  53                 continuation.succeeded(result);\r
  54     }\r
  55     \r
  56     public void cancel() {\r
  57         failWith(new CancellationException());\r
  58     }\r
  59     \r
  60     public T get() throws Exception {\r
  61         doneGate.await();\r
  62         if(exception != null)\r
  63             throw exception;\r
  64         return result;\r
  65     }\r
  66 }\r